Protecting your trees from winter damage

Sunscald in Boise area

Sun scald is the most common winter damage we get in this area, especially on young trees.

Sunscald is recognized as a freezing and thawing process that cracks and damages the bark on young trees from November through February.

Our climate is getting more humid in the winter, this humidity penetrates young bark making in soaked in moisture. This moisture does not evaporate but is held by the bark and easily freezes in that it is very exposed. That freezing process naturally expands the bark just as it does if you put a water bottle in your freezer. Then the sun comes out and thaws the bark which contracts the bark.

The young bark is pliable and can withstand this process a few times, but then we get days where we hover right at freezing, the sun hitting the bark on the SW side quickly melts the frost, then goes behind a cloud and the freezing temperature quickly freezes and expands the bark. This can happen dozens of times during the day and the bark begins to tear and damage the fragile cell structure in the tissue below the cork bark. That cell structure is the phloem and xylem layer which is equivalent to our veins and arteries. These arteries become damaged and when the tree goes into spring, the arteries do not support that area and the visible tissue death can be seen as in the photo above.

Here is a video I did with a close up of a tree here in the Boise area Click Here.

Fortunately Sunscald is not difficult to prevent, you just have to remember to do it. The basic idea is you want to shield the tree bark from the sun so it will not freeze and thaw quickly. You might have seen old orchards with the bark painted white, this was the early method however paint is not good for tree cells. A wrap is often used but this can harbor moisture and insects, both of which can do damage to the young bark. What I like is simple cardboard like the cardboard you probably had around the tree when you got it from the nursery.

 

Or you can take plastic pipe like this but be sure to not tear the bark when getting it around the tree.

 

 

Planting a Tree in late fall

The Good and the Bad of planting trees in the fall

Fall is cooler which means less stress on trees, however this doesn't mean it's the best time to plant any kind of tree.

Keep in mind that Evergreens, like pine trees, are actually going to work hard all winter long, so they will still have growth stress. With that in mind, they still would rather work hard in cooler weather than 100 degree heat.

Decidua, or leaf trees, drop their leaves and shut down into dormancy in the winter which means they are doing little to no work so little to no stress. So decidua trees do well planted in the fall.

Now the bad; no mater the type of tree, water is still an issue. Far less for the leaf tree but you don't want the tree to wake up in a completely dry base around the new feeder roots pushing out. You can't see these roots so you will not know when they need water. Often it is far before the lawn irrigation is started up and we forget to help these newly planted trees in early spring.

For the Evergreen tree, they will need slow watering all winter which is near impossible if we are having freezing nights which will break the hose.

The answer I have used is to encourage fall planting but insist that hose is kept in the garage ready to go out and water the trees. This is done at the time of planting for the decidua then put on the calendar to do once in late February and once a week in March and April until the water is turned on. For the Evergreen I want to water it once a week all through winter if at all possible. This doesn't have to be a flood of water, a soaker hose for four or five hours is usually enough. But do not guess, get the water meter we talk about at www.diylawntime.blogspot.com and check to be sure.